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Visually Aligned Monochromatic Lamina Detector

IP.com Disclosure Number: IPCOM000088859D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Gaston, CA: AUTHOR [+2]

Abstract

As a transparent thin film changes in thickness, the interference between light reflected from its two surfaces changes between constructive and destructive interference for each quarter-wavelength change in film thickness. This phenomenon is used in a wide variety of thickness-monitoring instruments.

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Visually Aligned Monochromatic Lamina Detector

As a transparent thin film changes in thickness, the interference between light reflected from its two surfaces changes between constructive and destructive interference for each quarter-wavelength change in film thickness. This phenomenon is used in a wide variety of thickness-monitoring instruments.

The optical configuration illustrated in the figure has many advantages over previous systems. One advantage is the telescopic viewing system which permits an operator to see precisely where the sensing beam strikes the target. (The laser-blocking filter passes just enough of the laser beam to produce a bright spot in the image of the target surface.) If the entire system is translated in the plane perpendicular to the target beam, the operator can select visually any desired portion of the target for sensing, and do so with great accuracy.

Although the relatively large focusing lens permits operation as long as some portion of the target beam is reflected back into the lens aperture, optimum viewing and sensitivity are achieved when the target beam is perpendicular to the target surface. The adjustable aiming mirror permits changing the beam angle without tilting the entire system, and the alignment aperture assists in determining visually when beam and target are perpendicular. (As the alignment aperture is closed down, the visible illuminated area shrinks. The aiming mirror is adjusted to keep this bright spot center...